.tip

Feb 14, 2026 · one of the small things

git bisect run finds the bad commit while you make tea

If you've got a command that fails on the broken version and passes on the good one, bisect can drive itself.

git bisect start HEAD v2.3.0
git bisect run pnpm test -- --filter checkout

It checks out the middle commit, runs the command, reads the exit code, and repeats, so two hundred commits take eight runs. The command can be a script that builds, starts the app and curls it, as long as it exits non-zero on the bug.

gitdebugging

~/tips/today — 2026-10-19

~cat tips/today

Never build an index on a live table without CONCURRENTLY

postgresqlmigrations

A plain CREATE INDEX takes a lock that blocks every write to the table for the whole build. On a big table that means minutes of outage that look like a hung app.

CREATE INDEX CONCURRENTLY orders_customer_idx ON orders (customer_id);

It's slower and can't run inside a transaction, so you'll have to tell your migration tool. If it fails halfway, it leaves an invalid index behind, so check pg_index.indisvalid and drop it before you retry.

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